Absence of gravin-mediated signaling inhibits development of high-fat diet-induced hyperlipidemia and atherosclerosis

Atractylodes macrocephala Rhizoma alleviates blood hyperviscosity induced by high-fat, high-sugar, and high-salt diet by inhibiting gut-liver inflammation and fibrinogen synthesis

ETHNOPHARMACOLOGICAL RELEVANCE

Unhealthy dietary patterns and lifestyle changes have been linked to increased blood viscosity, which is recognized as an important pathogenic factor in cardiovascular and cerebrovascular diseases. The underlying mechanism may involve chronic inflammation resulting from intestinal barrier disruption induced by unhealthy diets. The rhizome of Atractylodes macrocephala Koidz. (Called Baizhu in China), is a well-used "spleen-reinforcing" traditional Chinese medicinal herb used for thousands of years. Previous research has demonstrated its multiple gastrointestinal health benefits and its ability to regulate metabolic disorders. However, the effects of Baizhu on blood hyperviscosity induced by long-term unhealthy diets remain unclear.

AIM OF THE STUDY

This study aimed to investigate the effects of the aqueous extract of Baizhu on blood hyperviscosity induced by unhealthy diet and to explore the possible mechanisms.

MATERIALS AND METHODS

The blood hyperviscosity model in SD rats was established utilizing a high-fat, high-sugar, and high-salt diet (HFSSD). Subsequently, the rats underwent a twelve-week intervention with varying doses of Baizhu and a positive control. To evaluate the efficacy of Baizhu on blood hyperviscosity in model rats, we measured behavioral index, hemorheological parameters, inflammatory cytokines, hematology, adhesion molecules, as well as biochemical indicators in serum and liver. We also assessed the pathological states of the colon and liver. Furthermore, Western blotting, ELISA, IHC, and qRT-PCR were used to determine the effect of Baizhu on the IL-6/STAT3/ESRRG signaling pathway and FIB synthesis.

RESULTS

The intervention of Baizhu showed evident attenuating effects on blood viscosity and microcirculation disorders, and exhibit the capacity to moderately modulate parameters including grip, autonomous activities, vertigo time, TC, TG, LDL-c, inflammatory factors, adhesion factors, hematological indicators, etc. At the same time, it reduces liver lipid droplet deposition, restores intestinal integrity, and lowers LPS level in the serum. Subsequent experimental results showed that Baizhu downregulated the expression of TLR4 and NF-κB in colon tissue, as well as the expression of IL-6, TLR4, p-JAK2, p-STAT3, and ESRRG in liver tissue. Finally, we also found that Baizhu could regulate the levels of FIB in plasma and liver.

CONCLUSION

Baizhu protects HFSSD-induced rats from blood hyperviscosity, likely through repairing the intestinal barrier and inhibiting LPS/TLR4-associated liver inflammatory activation, thus suppressing FIB synthesis through the downregulation of IL-6/STAT3/ESRRG pathway.

Novel insight into the role of A-kinase anchoring proteins (AKAPs) in ischemic stroke and therapeutic potentials

Ischemic stroke, a devastating disease associated with high mortality and disability worldwide, has emerged as an urgent public health issue. A-kinase anchoring proteins (AKAPs) are a group of signal-organizing molecules that compartmentalize and anchor a wide range of receptors and effector proteins and have a major role in stabilizing mitochondrial function and promoting neurodevelopmental development in the central nervous system (CNS). Growing evidence suggests that dysregulation of AKAPs expression and activity is closely associated with oxidative stress, ion disorder, mitochondrial dysfunction, and blood-brain barrier (BBB) impairment in ischemic stroke. However, the underlying mechanisms remain inadequately understood. This review provides a comprehensive overview of the composition and structure of A-kinase anchoring protein (AKAP) family members, emphasizing their physiological functions in the CNS. We explored in depth the molecular and cellular mechanisms of AKAP complexes in the pathological progression and risk factors of ischemic stroke, including hypertension, hyperglycemia, lipid metabolism disorders, and atrial fibrillation. Herein, we highlight the potential of AKAP complexes as a pharmacological target against ischemic stroke in the hope of inspiring translational research and innovative clinical approaches.

AKAP12 Upregulation Associates With PDE8A to Accelerate Cardiac Dysfunction

BACKGROUND

In heart failure, signaling downstream the β2-adrenergic receptor is critical. Sympathetic stimulation of β2-adrenergic receptor alters cAMP (cyclic adenosine 3',5'-monophosphate) and triggers PKA (protein kinase A)-dependent phosphorylation of proteins that regulate cardiac function. cAMP levels are regulated in part by PDEs (phosphodiesterases). Several AKAPs (A kinase anchoring proteins) regulate cardiac function and are proposed as targets for precise pharmacology. AKAP12 is expressed in the heart and has been reported to directly bind β2-adrenergic receptor, PKA, and PDE4D. However, its roles in cardiac function are unclear.

METHODS

cAMP accumulation in real time downstream of the β2-adrenergic receptor was detected for 60 minutes in live cells using the luciferase-based biosensor (GloSensor) in AC16 human-derived cardiomyocyte cell lines overexpressing AKAP12 versus controls. Cardiomyocyte intracellular calcium and contractility were studied in adult primary cardiomyocytes from male and female mice overexpressing cardiac AKAP12 (AKAP12OX) and wild-type littermates post acute treatment with 100-nM isoproterenol (ISO). Systolic cardiac function was assessed in mice after 14 days of subcutaneous ISO administration (60 mg/kg per day). AKAP12 gene and protein expression levels were evaluated in left ventricular samples from patients with end-stage heart failure.

RESULTS

AKAP12 upregulation significantly reduced total intracellular cAMP levels in AC16 cells through PDE8. Adult primary cardiomyocytes from AKAP12OX mice had significantly reduced contractility and impaired calcium handling in response to ISO, which was reversed in the presence of the selective PDE8 inhibitor (PF-04957325). AKAP12OX mice had deteriorated systolic cardiac function and enlarged left ventricles. Patients with end-stage heart failure had upregulated gene and protein levels of AKAP12.

CONCLUSIONS

AKAP12 upregulation in cardiac tissue is associated with accelerated cardiac dysfunction through the AKAP12-PDE8 axis.

Development of stem cell therapy for atherosclerosis

Cardiovascular disease (CVD) has a high incidence and low cure rate worldwide, and atherosclerosis (AS) is the main factor inducing cardiovascular disease, of which lipid deposition in the vessel wall is the main marker of AS. Currently, although statins can be used to lower lipids and low-density lipoprotein (LDL) in AS, the cure rate for AS remains low. Therefore, there is an urgent need to develop new therapeutic approaches, and stem cells are now widely studied, while stem cells are a class of cell types that always maintain the ability to differentiate and can differentiate to form other cells and tissues, and stem cell transplantation techniques have shown efficacy in the treatment of other diseases. With the establishment of cellular therapies and continued research in stem cell technology, stem cells are also being used to address the problem of AS. In this paper, we focus on recent research advances in stem cell therapy for AS and briefly summarize the relevant factors that induce the formation of AS. We mainly discuss the efficacy and application prospects of mesenchymal stem cells (MSCs) for the treatment of AS, in addition to the partial role and potential of exosomes in the treatment of AS. Further, provide new ideas for the clinical application of stem cells.

Curcumin nanoemulsion counteracts hepatic and cardiac complications associated with high-fat/high-fructose diet in rats

The relationship between the incidence of cardiovascular abnormalities and non-alcoholic fatty liver disease (NAFLD) has long been postulated. Curcumin (CUR) is a potential anti-atherosclerotic agent but its poor water solubility hinders its pharmacological use. Therefore, the present study aimed to investigate the effect of formulation of CUR nanoemulsion prepared using the spontaneous emulsification technique on high fat high fructose (HFHF)-induced hepatic and cardiac complications. Fifty Wistar rats were divided into five groups. CUR nanoemulsion at doses of 5 and 10 mg/kg and conventional powdered CUR at a dose of 50 mg/kg were orally administered daily to rats for two weeks, and compared with normal control and HFHF control. Results revealed that the high dose level of CUR nanoemulsion was superior to conventional CUR in ameliorating the HFHF-induced insulin resistance status and hyperlipidemia, with beneficial impact on rats' recorded electrocardiogram (ECG), serum aspartate aminotransferase (ALT) and alanine aminotransferase (AST) levels, leptin, adiponectin, creatine phosphokinase, lactate dehydrogenase and cardiac troponin-I. In addition, hepatic and cardiac oxidative and nitrosative stresses, oxidative DNA damage and disrupted cellular energy statuses were counteracted. Results were also confirmed by histopathological examination. PRACTICAL APPLICATIONS: The use of curcumin nanoemulsion could be beneficial in combating hepatic and cardiac complications resulting from HFHF diets.

Physiologic and pathophysiologic roles of AKAP12

A kinase anchoring protein (AKAP) 12 is a scaffolding protein that improves the specificity and efficiency of spatiotemporal signal through assembling intracellular signal proteins into a specific complex. AKAP12 is a negative mitogenic regulator that plays an important role in controlling cytoskeletal architecture, maintaining endothelial integrity, regulating glial function and forming blood-brain barrier (BBB) and blood retinal barrier (BRB). Moreover, elevated or reduced AKAP12 contributes to a variety of diseases. Complex connections between AKAP12 and various diseases including chronic liver diseases (CLDs), inflammatory diseases and a series of cancers will be tried to delineate in this paper. We first describe the expression, distribution and physiological function of AKAP12. Then we summarize the current knowledge of different connections between AKAP12 expression and various diseases. Some research groups have found paradoxical roles of AKAP12 in different diseases and further confirmation is needed. This paper aims to assess the role of AKAP12 in physiology and diseases to help lay the foundation for the design of small molecules for specific AKAP12 to correct the pathological signal defects.

Targeted disruption of PKC from AKAP signaling complexes

Protein Kinase C (PKC) is a member of the AGC subfamily of kinases and regulates a wide array of signaling pathways and physiological processes. Protein-protein interactions involving PKC and its scaffolding partners dictate the spatiotemporal dynamics of PKC activity, including its access to activating second messenger molecules and potential substrates. While the A Kinase Anchoring Protein (AKAP) family of scaffold proteins universally bind PKA, several were also found to scaffold PKC, thereby serving to tune its catalytic output. Targeting these scaffolding interactions can further shed light on the effect of subcellular compartmentalization on PKC signaling. Here we report the development of two hydrocarbon stapled peptides, CSTAD5 and CSTAD6, that are cell permeable and bind PKC to disrupt PKC-gravin complex formation in cells. Both constrained peptides downregulate PMA-induced cytoskeletal remodeling that is mediated by the PKC-gravin complex as measured by cell rounding. Further, these peptides downregulate PKC substrate phosphorylation and cell motility. To the best of our knowledge, no PKC-selective AKAP disruptors have previously been reported and thus CSTAD5 and CSTAD6 are novel disruptors of PKC scaffolding by AKAPs and may serve as powerful tools for dissecting AKAP-localized PKC signaling.

Proteomics analysis of adipose depots after intermittent fasting reveals visceral fat preservation mechanisms

Intermittent fasting is a beneficial dietary treatment for obesity. But the response of each distinct adipose depot is currently poorly defined. Here we explore the response of key adipose depots to every-other-day fasting (EODF) in mice using proteomics. A key change in subcutaneous white adipose tissue (scWAT) and visceral WAT (vWAT) depots is an increase in mitochondrial protein content after EODF. This effect is correlated with increased fatty acid synthesis enzymes in both WAT depots but not in brown adipose tissue. Strikingly, EODF treatment downregulates lipolysis specifically in vWAT, mediated by a large decrease in the abundance of the catecholamine receptor (ADRB3). Together, these changes are important for preservation of the visceral lipid store during EODF. Enrichment analysis highlights downregulation of inflammatory collagen IV specifically in vWAT, allowing improved insulin sensitivity. This resource for adipose-depot-specific fasting adaptations in mice is available using a web-based interactive visualization.

Exosomes: Multifaceted Messengers in Atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis (AS) is a chronic inflammatory disease that contributes to the development of coronary artery disease, which has become a leading health burden worldwide. Though several strategies such as pharmacological treatment, exercise intervention, and surgery have been used in clinical practice, there is still no effective strategy to cure AS. Exosomes are extensively studied both as diagnostic markers as well as for therapeutic purposes due to their role in pathological processes related to AS. To elucidate the role of exosomes in AS and thus provide a new insight into AS therapy, we review recent advances concerning exosome targets and their function in mediating intercellular communication in AS, and expect to provide a reference for novel effective strategies to cure AS.

RECENT FINDINGS

Exosomes exert important roles in the diagnosis, development, and potential therapy of AS. For AS development, (1) activation of CD-137 in endothelial cells represses exosomal-TET2 production, causing a phenotypic switch of vascular smooth muscle cells (VSMC) and promoting plaque formation; (2) exosomal-MALTA1 derived from endothelial cells causes neutrophil extracellular traps (NETs) and M2 macrophage polarization, which aggravates AS; and (3) exosomal-miR-21-3p derived from macrophages inhibits PTEN expression and further promotes VSMC migration/proliferation, leading to AS development. For AS diagnosis, plasma exosomal-miR30e and miR-92a are considered to be potential diagnostic markers. For AS therapy, adipose mesenchymal stem cell-derived exosomes protect endothelial cells from AS aggravation, via inhibiting miR-342-5p. Exosome-mediated cross-talk between different cells within the vasculature exerts crucial roles in regulating endothelial function, proliferation and differentiation of vascular smooth muscle cells, and platelet activation as well as macrophage activation, collectively leading to the development and progression of AS. Exosomes can potentially be used as diagnostic biomarkers and constitute as a new therapeutic strategy for AS.

AKAP12 Signaling Complex: Impacts of Compartmentalizing cAMP-Dependent Signaling Pathways in the Heart and Various Signaling Systems

Heart failure is a complex clinical syndrome, represented as an impairment in ventricular filling and myocardial blood ejection. As such, heart failure is one of the leading causes of death in the United States. With a mortality rate of 1 per 8 individuals and a prevalence of 6.2 million Americans, it has been projected that heart failure prevalence will increase by 46% by 2030. Cardiac remodeling (a general determinant of heart failure) is regulated by an extensive network of intertwined intracellular signaling pathways. The ability of signalosomes (molecular signaling complexes) to compartmentalize several cellular pathways has been recently established. These signalosome signaling complexes provide an additional level of specificity to general signaling pathways by regulating the association of upstream signals with downstream effector molecules. In cardiac myocytes, the AKAP12 (A-kinase anchoring protein 12) scaffolds a large signalosome that orchestrates spatiotemporal signaling through stabilizing pools of phosphatases and kinases. Predominantly upon β-AR (β2-adrenergic-receptor) stimulation, the AKAP12 signalosome is recruited near the plasma membrane and binds tightly to β-AR. Thus, one major function of AKAP12 is compartmentalizing PKA (protein kinase A) signaling near the plasma membrane. In addition, it is involved in regulating desensitization, downregulation, and recycling of β-AR. In this review, the critical roles of AKAP12 as a scaffold protein in mediating signaling downstream GPCRs (G protein-coupled receptor) are discussed with an emphasis on its reported and potential roles in cardiovascular disease initiation and progression.

Liraglutide improves lipid metabolism by enhancing cholesterol efflux associated with ABCA1 and ERK1/2 pathway

Background

Reverse cholesterol transport (RCT) is an important cardioprotective mechanism and the decrease in cholesterol efflux can result in the dyslipidemia. Although liraglutide, a glucagon like peptide-1 analogue, has mainly impacted blood glucose, recent data has also suggested a beneficial effect on blood lipid. However, the exact mechanism by which liraglutide modulates lipid metabolism, especially its effect on RCT, remain undetermined. Hence, the aim of the present study was to investigate the potential impacts and potential underlying mechanisms of liraglutide on the cholesterol efflux in both db/db mice and HepG2 cells.

Methods

Six-week old db/db mice with high fat diet (HFD) and wild type mice were administered either liraglutide (200 μg/kg) or equivoluminal saline subcutaneously, twice daily for 8 weeks and body weight was measured every week. After the 8-week treatment, the blood was collected for lipid evaluation and liver was obtained from the mice for hematoxylin–eosin (HE) staining, red O staining and Western blotting. Cholesterol efflux was assessed by measuring the radioactivity in the plasma and feces after intraperitoneal injection of ³H-labeled cholesterol. HepG2 Cells were treated with different concentrations of glucose (0, 5, 25, and 50 mmol/L) with or without liraglutide (1000 nmol/L) for 24 h. The intracellular cholesterol efflux was detected by BODIPY-cholesterol fluorescence labeling. Real-time PCR or Western blotting was used to examine the expression levels of ABCA1, ABCG1 and SR-B1.

Results

Liraglutide significantly decreased blood glucose, serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C). It also reduced liver lipid deposition in db/db mice fed with HFD. Moreover, the movement of ³H-cholesterol from macrophages to plasma and feces was significantly enhanced in db/db mice fed with HFD after liraglutide adminstration. In vitro study, liraglutide could promote the cholesterol efflux of HepG2 cells under high glucose, and also increase the expression of ABCA1 by activating the ERK1/2 pathway.

Conclusions

Liraglutide could improve lipid metabolism and hepatic lipid accumulation in db/db mice fed with HFD by promoting reversal of cholesterol transport, which was associated with the up-regulation of ABCA1 mediated by the ERK1/2 phosphorylation.